phyics Lense

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2010-01-23 10:13 pm

an object is placed in front of a convex lens of focal length 20cm find graphically the position nature and linear magnification of the object distance is 60cm

更新1:

how to find postion? how to find nature? how to find linear magnification? how to find magnification if focal length 20 is given and object distancce 60cm is given?

更新2:

when a toy is placed 3 cm in front of convex lens with focal length 6 cm how to find the magnification? how is the properties of he image? placed 20cm in front of a concave lens focal length of the lens is 25how to find the position and how to state the nature of the image distance?

回答 (2)

用戶18354

2010-02-02 10:23 pm

無最佳解答

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天同

2010-01-23 11:07 pm

Assume the object is an arrow, located at position 60 cm from the lens.
You could draw two light rays from the top of the arrow,
- the first ray passes through the centre of the lens, this ray is not refracted by the lens, so it remains as a striaght line;
- the second ray is parallel to the principal axis, after refraction at the lens, it passes through the focus of the lens.

The intersection of these two light rays gives the position of the image of the top of the arrow.

After completion of the diagram, you should be able to obtain the following results by measurements on the diagram,

image is real, inverted, 30 cm behind the lens, size is half that of the object.

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